adolescence

Whether you are frequently wearing Lulu Lemon gear or not, it is difficult to miss the assurgency of yoga as a popular fitness activity. Taking the emphasis away from measurement-based exercise, like marathon running or bench presses, yoga is first and foremost about flexibility. Breathe. Stretch. Relax. Repeat.

In a similar way, one branch of emotion research over the past decade has begun to show the benefits of emotional flexibility.

In the most general sense, flexibility requires change in response to an event. With objects, as with bodies, this is often reflected in bending or changing shape somehow in order to accommodate shifting conditions without losing integrity. The opposite, then, is rigidity, where the object or body resists and retains its pre-existing shape. At its core, the concept of flexibility/rigidity is all about adaptation to local conditions in the environment.

With emotional flexibility, the same distinctions apply.

From moment-to-moment, emotions ebb and flow in a constant stream from one state to the next. A simple ritual of reading the newspaper can create a sequence of anger at a politician, sadness about the passing of a favorite celebrity, and a chuckle from the cartoon on page 12. Interacting with other people also punctuates that ebb and flow through complaints, joking, or interest.

A group of researchers led by Peter Kuppens and Peter Koval have examined this ebb and flow as emotional inertia, or the tendency to remain in an emotional state, even when conditions are changing (rigidity). To measure inertia, they use a type of correlation called an autocorrelation, which refers to the degree of correlation between a first moment (let’s call it time 1) with the next moment (let’s call it time 2) and so on. Higher autocorrelations of emotional states means that a person’s emotions are similar across multiple instances and that they are not changing very much. This indicates greater rigidity. Imagine being stuck in an angry mood all day and not reacting positively when you see an old friend. This would be pretty rigid. Now you might think that the reverse could be a good thing—getting stuck in a positive mood in the face of negative events, but this can be rigid too. Imagine you stay positive in the face of a slew of negative events during a really bad day (e.g., you get passed up for a promotion, you learn a friend is sick, you get in a fender-bender on the way home). This might buffer you from the effects of the negative events, but staying positive might also mean that you’re not appropriately reacting to those events or doing anything to change them. It might be more adaptive to get sad or angry when you get passed over for a promotion because it will make you try harder in the future. Consistent with this logic, a series of studies demonstrated that higher inertia, of both positive and negative emotions, has been associated with rumination and low self-esteem, but especially depression and the onset of depression in adolescents. Getting stuck, even in positive states, is not desirable.

But individual’s emotions don’t rise and fall in a vacuum. Most of the time, one’s emotions are ebbing and flowing because of interacting with someone else, whose emotions are also ebbing and flowing. Now add a third person. How can we measure that complexity?

My research group examines emotional flexibility among two or three interacting people by first viewing them as complex dynamic systems. Without getting too technical, the idea is that two people – let’s call them a “dyad” (as opposed to a monad or triad) – form a system of mutual influence on each other. The emotional patterns or “dynamics” of the interaction reveal the nature of that system. At a relatively simple level, we can characterize these dyadic systems as more or less flexible by measuring (1) the range of emotional states experienced; (2) the number of changes in emotional states experienced across time; and (3) the tendency to have short vs. long durations in emotional states. The image below shows the difference between a flexible mother-child dyad discussing a conflict they have at home and a rigid dyad doing the same thing.

These state space grids depict all possible emotional states of the mother (horizontal axis) and child (vertical axis) along 5 categories of different types of emotional experiences (e.g., a Hi Pos experience might be feeling excited whereas a Lo Pos experience might be feeling calm). This is simplified for the sake of illustration but can be done with any type of emotional experiences. Each box or cell of the grid represents one state; for example, the bottom left cell is for those moments when both mother and child are in highly negative states (e.g., angry, anxious). The dots and blue lines trace the sequence of those states across the interaction, and the size of the dot indicates how long they were in that particular state. Thus, you can see that the flexible dyad on the left has a greater range of states, (more cells occupied), makes more transitions (more lines), and has shorter durations (smaller dots) than the dyad on the right. The pattern for the flexible dyad on the left is like a movie, with the parent and child sharing and exchanging emotional expressions in fluid motions. The pattern for the rigid dyad on the right is like a series of still photographs, with the parent and child posing for a while and then shifting poses only occasionally. Using this technique, my colleagues and I have been able to show how:

Although it is not immediately intuitive, these studies indicate that these effects occur above and beyond emotional intensity or the emotions being experienced – inertia and rigidity in both positive and negative states is problematic. The take home message is clear: experiencing and expressing emotions in a flexible way is generally indicative of healthy functioning in day-to-day life.

Colloquially, it is common to use flexibility and rigidity when describing others. We praise people for going with the flow, chilling out, or rolling with the punches, but then denigrate the stick in the mud or someone stuck in a rut. Perhaps what we are picking up on is a person’s ability to move in and out of emotional states with relative ease. In addition to making sure to do your sun salutations or enough reps, it is just as important to stretch your emotional muscles.

The internalizing disorders—anxiety and depression—are a major human blight. According to the World Health Organization and National Institute of Mental Health, depression is responsible for more years lost to illness and disability than any other medical condition, including such familiar scourges as diabetes and chronic respiratory disorders. Anxiety disorders are the most common family of psychiatric disorder in the United States and rank sixth as a worldwide cause of disability. These disorders, which commonly co-occur, also impose a substantial and largely hidden burden on the global economy: hundreds of billions of dollars in healthcare costs and lost productivity each year. Unfortunately, existing therapeutic approaches are inconsistently effective or, in the case of many pharmaceutical approaches, are associated with significant side effects. Not surprisingly, the internalizing disorders have become an important priority for clinicians, economists, research funding agencies, and policy makers.

The internalizing disorders generally have their roots in the first three decades of life and there is clear evidence that children with a fearful, shy, or anxious temperament are more likely to suffer from anxiety disorders, major depression, or both as they grow older. As a postdoctoral fellow in Ned Kalin’s lab at the University of Wisconsin and, more recently, as the director of my own lab at the University of Maryland, I’ve used a range of tools and techniques to understand the brain systems that contribute to extreme anxiety early in life. Building on a tradition that dates back to pioneering studies at Wisconsin by Harry Harlow, Karl Pribram, and others, much of the work that I conducted as a postdoc used nonhuman primates to model and understand key features of childhood anxiety. Young rhesus monkeys are useful for deciphering the brain circuits that underlie childhood anxiety. Owing to the relatively recent evolutionary divergence of humans and Old World monkeys (~25 million years ago), the brains of monkeys and humans are biologically similar. Similar brains endow monkeys and children with a common repertoire of social and emotional behaviors, which makes it possible to measure anxiety in monkeys using procedures similar to those used with kids. Another virtue of working with monkeys is the opportunity to collect high-resolution measures of brain activity (using positron emission tomography or PET) while the animals freely respond—hiding in the corner, barking, and so on—to naturalistic threats, such as an unfamiliar human ‘intruder’s’ profile. This would be difficult or impossible to do in children and, somewhat surprisingly, has rarely been attempted in adults (most human imaging studies use fMRI, which requires that the subject remain dead still throughout the scan).

Large-scale brain imaging studies, each including hundreds of young monkeys—in humans terms, roughly equivalent to children and teens—show that anxious individuals respond to signs of potential threat with heightened activity in a number of brain regions. For present purposes, I’ll focus on the contribution of the amygdala, a small, almond-shaped region buried beneath the temporal lobe of the brain (the red regions in the accompanying animation).

Collectively, these studies teach us that amygdala activity systematically differs across individuals. Some individuals show chronically elevated activity; others consistently show much lower levels. Notably, elevated activity is associated with exaggerated reactions to potential danger: Monkeys with higher levels of metabolic activity in the amygdala tend to show higher levels of the stress hormone cortisol and to freeze longer (in an attempt to evade detection) in encounters with the human intruder. Like many other qualities that distinguish one individual from another, work by our group demonstrates that amygdala activity is:

1. Consistent over time and context: We can think of amygdala activity as a trait, like personality or IQ.

2. Heritable: Amygdala activity partially reflects the influence of genes. Parents marked by higher levels of amygdala activity are more likely to have offspring with this trait.

Of course, like any brain imaging study, it’s important to remember that these results do not let us to claim that the amygdala causes anxiety. From this perspective, it is reassuring that mechanistic work in monkeys and rodents demonstrates that it does: selective lesions and other biological manipulations of the amygdala sharply reduce (but do not entirely abolish) anxiety (see for example this very recent rodent study). This is consistent with observations of a handful of human patients with near-complete amygdala damage. For example, one relatively well-known patient (identified as ’SM,’ to protect her identity), has normal intellect, but reports a profound lack of fear and anxiety in response to scary movies, haunted houses, tarantulas, and snakes.

“She has been held up at knife point and at gun point, she was once physically accosted by a woman twice her size, she was nearly killed in an act of domestic violence, and on more than one occasion she has been explicitly threatened with death…What stands out most is that, in many of these situations, SM’s life was in danger, yet her behavior lacked any sense of desperation or urgency. Police reports…corroborate SM’s recollection of these events and paint a picture of an individual who lives in a poverty-stricken area replete with crime, drugs, and danger…Moreover, it is evident that SM has great difficulty detecting looming threats in her environment and learning to avoid dangerous situations.”

This and other evidence—spanning a range of species, populations, and measurement tools—indicates that anxious individuals’ exaggerated distress in the face of potential danger reflects hyper-reactivity in a brain circuit that includes the amygdala. Systematic differences in amygdala activity and connectivity first emerge early in life and can foretell the future development of anxious and depressive symptoms in humans. These and other observations suggest that enduring differences in amygdala function contribute to key features of childhood temperament, like shyness, and confer increased risk for the development of internalizing disorders, particularly among individuals exposed to stress or trauma. More importantly, this work lays a solid, brain-based foundation for developing better strategies for treating or even preventing these debilitating illnesses.

If you had to choose one event that epitomizes your experience as a teenager, what would it be? For me, I immediately think of that moment at the school dance while I was dancing with my middle school crush to November Rain by Guns n Roses. Our slow dancing skills were passable during the first part of the song, but then the tempo picked up … and let’s just say, we were not very smooth at adapting our dancing styles. Although I hope (for your sake) that the same thing didn’t happen to you, I’d bet that whatever memory you do conjure when you think back to your own adolescence is socially and emotionally charged.

It turns out that my adolescent experiences were completely typical of most adolescents—social experiences take on heightened emotional and motivational importance during adolescence as compared to other stages of life. In a study we conducted, we wanted to see how sensitive adolescents were to even the simplest, most innocuous social provocation: being looked at by a peer. During our study, we measured brain activity with functional magnetic resonance imaging in tandem with physiological arousal (measured with the skin conductance response—how much sweat is secreted on the skin during emotional events). We observed that even the simple act of being looked at by a peer was enough to induce heightened emotion reports, physiological responses, and brain activity in adolescents (when compared to adults and younger children). For instance, we saw biased activity in regions of the brain important for representing the emotional value of stimuli and in brain regions involved in thinking about ourselves (to read more, see here). All of these findings add up to the general conclusion that adolescents are highly attuned and reactive to their social environments – even very subtle ones – and that this fact influences a variety of their daily choices and feelings.

The author of this post at age 13 showing off her spiral perm.

What’s interesting about these findings is that they seem not to be unique to human adolescents. The term ‘adolescence’ is a sociocultural construct that refers only to humans, defined by simultaneous physical and psychological change that ends when an individual takes on adult roles in society (adolescence is most often defined as the approximate ages ~13-17 years). However, some aspects of biological changes during this age range, including hormone changes that define puberty, occur in other mammals as well. Some surprising results have arisen from the study of pubertal-linked changes in social behavior in non-human mammals. Pubertal rats enjoy ‘social play’ (kind of like wrestling) more frequently than adult rodents, and also seek out more novel and potentially thrilling experiences. Perhaps most intriguingly, rodents undergoing puberty also approach potential rewards (in this case, consuming alcoholic beverages) more when in social groups. Whereas adult mice spent the same amount of time consuming alcoholic substances when alone and with peer animals, juvenile animals in the pubertal stage spent more time consuming alcohol when in a cage with familiar peer animals. And it wasn’t just a motivation to consume the tasty cocktail before others got to it – they each had their own sipper.

What lessons can we learn from our furry friends about adolescence and the social potency that characterizes this age range? It is often assumed that peers take on heightened importance in adolescence due to overt concern about social status. However, it seems unlikely that such complicated, strategic motivations would drive rodents to behave differently around peers. This raises a second possibility, that there are “undercover” or non-deliberate ways that adolescents are influenced by social contexts. We believe that adolescents’ brains are biased to assign importance to social information, which imbues social settings with an extra boost in power to shape their feelings, motivations, and decisions. Although more research needs to be done to address questions like “why” and “how”, I guess that’s why I’m still mildly embarrassed by my tragic bout of dancing (and simultaneously thankful I grew up before the days of smartphone cameras).